The present invention relates to a single facer for making a single-faced corrugated sheet, and more particularly to a single facer of the type wherein a core paper sheet is corrugated by means of a pair of upper and lower corrugated rolls and has its crest portions applied with paste and then a liner introduced from a different direction is pasted on the corrugated core sheet while passing between the lower corrugated roll and a pressure roll to form a single-faced corrugated sheet.
At first, description will be made of a single-facer known in the prior art with reference to FIG. 1 which shows one example of the known single-facer of the above-mentioned type. In this figure, a core paper sheet 4 is introduced to a meshing point between an upper corrugated roll 1 and a lower corrugated roll 2 both of which have their circumferential surfaces machined into a corrugated configuration, and thereby the core paper sheet 4 is worked into a corrugated shape. Subsequently, the corrugated core paper sheet has its crest portions applied with paste by means of a paste application roll 7, and then it is urged against a liner 5 introduced to the single facer from a different direction and also is heated at an engaging portion between the lower corrugated roll 2 and a pressure roll 3. Thereby a single-faced corrugated sheet 8 is formed.
In addition, in the structure shown in FIG. 1, the upper corrugated roll 1 is mounted on an arm 9 via a bearing not shown. This arm 9 has one end swingably mounted on a frame 11 via a pivot pin 10, and has the other end connected to a rod of a cylinder 13 which is connected to a bracket 12 fastened to the frame 11. Also, the lower roll 2 is mounted on the frame 11 and the bracket 12 via a bearing not shown.
Owing to the above-described structure, the urging force between the upper corrugated roll 1 and the lower corrugated roll 2 which is necessitated for shaping the core paper sheet 4 into a corrugated shape, is obtained by the driving force of the cylinder 13. Within the upper corrugated roll 1, lower corrugated roll 2 and pressure roll 3 are respectively provided hollow spaces so that steam can be introduced into these hollow spaces for the purpose of promoting shaping of the core paper sheet 4 into a corrugated shape and pasting of the corrugated paper sheet with the liner 5.
A cross-section of a corrugated cardboard sheet is illustrated in FIG. 2. Generally, corrugated cardboard sheets are classified depending upon the shape of corrugation into A, B, C and E flute classes, which have respectively different heights H and different pitches P (See FIG. 2) of corrugation, and which are selectively employed depending upon uses.
However, in the single facer in the prior art, in the case of replacing the corrugated rolls for the purpose of making corrugated cardboard sheets of different classes, it is necessary to disassemble the bracket 12, pivot pin 10, steam pipings, etc. as shown in FIG. 1. It also is necessary to delay the replacement operation until the corrugated rolls and peripheral component parts, which have been held at a high temperature by the introduced steam during the previous corrugating operation, have cooled to a satisfactorily low temperature. Therefore, a replacement period of one to two days was necessitated. Due to the necessity of this replacement period, it was a common practice in the prior art that normally one single facer can make only one class of corrugated cardboard sheets.